Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$198.56	8.676%	$215.7871	$215.79	$215.80	$215.80
Purchase #2	$177.38	4.627%	$185.5874	$185.59	$185.60	$185.60
Purchase #3	$19.27	12.369%	$21.6535	$21.65	$21.65	$21.70
Purchase #4	$183.67	3.552%	$190.194	$190.19	$190.20	$190.20
Purchase #5	$110.81	3.344%	$114.5155	$114.52	$114.50	$114.50
Purchase #6	$49.25	12.124%	$55.2211	$55.22	$55.20	$55.20
Purchase #7	$249.40	4.606%	$260.8874	$260.89	$260.90	$260.90
7 purchase totals =	$988.34		$1,043.8460	$1,043.85	$1,043.85	$1,043.90